Ultra wideband (UWB) is a type of wireless system that uses a significant amount of frequency spectrum. For example, bands described in the WiMedia UWB specification have bandwidths of 508 MHz. Sometimes a UWB system shares the wireless medium with other (e.g., narrowband) wireless systems by creating a notch in the UWB transmission signal where the other wireless system is operating. For example, some narrowband wireless systems have bandwidths on the order of 1 to 20 MHz and in some cases a notch (e.g., approximately 10 or 30 MHz wide) is created by a UWB system at the frequency spectrum where the other wireless system is operating.
One issue associated with creating a notch is leakage from a local oscillator operating at the UWB carrier frequency (e.g., center frequency of a band). Some regulatory agencies in Europe and/or Japan are discussing levels of suppression for UWB systems that are lower than previously required for other systems. Although there may exist some techniques for removing or suppressing local oscillator leakage (e.g., developed for narrowband systems), these techniques may not necessarily be able to remove or suppress local oscillator leakage to a degree sufficient for some proposed requirements. For example, the notch (which is often added in the digital domain) may not be able to reduce or remove local oscillator leakage since it is added afterwards. In the analog domain, using a filter to remove local oscillator leakage may be undesirable since such a filter would have to be operated at very high frequencies (e.g., in the range of 3.96 GHz if a 3.96 GHz carrier frequency is used) and would need to be quite narrow so that information in adjacent frequencies is not removed. It would be desirable to develop new techniques for dealing with local oscillator leakage.